Optical recording medium with different wobble characteristics between the user data area and the lead-out area

ABSTRACT

An optical recording medium has a user data area and a lead-out area, wherein the user data area and the lead-out area each has grooves and lands formed thereon. Wobbles are formed on at least one lateral surface of grooves of the user data area and the lead-out area, and configured such that wobble characteristics are made different between the user data area and the lead-out area. Different types of wobbles are formed on the grooves of either the user data area or the lead-out area, thereby preventing an optical pickup that performs recording/reproduction from deviating from the user data area. Also, in a multi-layer optical recording medium, a whole area of a recording layer is configured to have a same condition, thereby preventing deterioration in reproduction and/or recording due to a difference in light power transmittance of another recording layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a Continuation Application of U.S.application Ser. No. 10/007,655, filed Dec. 10, 2001, now pending. Thisapplication claims the benefit of Korean Application No. 2001-34377,filed Jun. 18, 2001, in the Korean Industrial Property Office, thedisclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to an optical recording medium, andmore particularly, to an optical recording medium having wobbles formedon at least one lateral surface of grooves of a user data area andgrooves of a lead-out area, and configured such that wobblecharacteristics are made different between the user data area and thelead-out area.

[0004] 2. Description of the Related Art

[0005] In general, optical recording media are widely employed asinformation recording media for an optical pickup device forrecording/reproducing information. The optical recording media areclassified into read-only-memory (ROM) compact discs (CDs) and digitalversatile discs (DVDs) according to information recording capacity.Further, a DVD disc capable of writing, erasing and reading informationcan be sub-divided into a digital versatile disc-random access memory(DVD-RAM) disc and a digital versatile disc-rewritable (DVD-RW) disc.

[0006] In such a DVD-RAM or DVD-RW disc, as shown in FIG. 1, there is alead-in area 10 in which read only data, such as disc size, number oftrack layers on a readable plane or illegal copy preventing information,is recorded, a user data area 20 in which user data can be repeatedlyread and/or written, and a lead-out area 30 in which other disc-relatedinformation is recorded.

[0007] As indicated by a portion “C” of FIG. 1, there are grooves 23 andlands 25 alternatively formed in the user data area 20, so as to performrecording and/or reproducing information marks 27 along a predeterminedtrack. In FIG. 1, reference numeral 40 denotes a reproduction beam. Fromenlarged portions of the lead-in area 10 (“A”) and the lead-out area 30(“B”), it is confirmed that physical pits 15, which is read only data,are formed thereon. Here, the lead-out area 30 performs variousfunctions. For example, the lead-out area 30 guards an optical pickup soas not to deviate from a user data area while the optical pickupperforms recording/reproduction.

[0008] In particular, as shown in FIG. 2, in a dual-layer opticalrecording medium having a first recording layer L0 and a secondrecording layer L1 of opposite track paths, the lead-out area 30 allowsan optical pickup to keep performing tracking during interlayer jumpingfrom the outermost circumference of the first layer L0 to the outermostcircumference of the second layer L1 without deviating from the trackpaths. The opposite tracks are sequentially addressed from the innercircumference of the first recording layer L0 to the outer circumferencethereof, and then from the outer circumference of the second recordinglayer L1 to the inner circumference thereof.

[0009] In a dual-layer ROM disc, an area serving as a lead-out areavaries according to the reproduction method of a second layer. In caseof a dual-layer ROM disc having opposite track paths, a middle area isseparately provided at each of the outer circumferences of the first andsecond recording layers. However, in case of a rewritable opticalrecording medium, both pits and grooves can be used Therefore, in caseof dual layer rewritable optical recording media, recording power isaffected by the physical geometry of the first recording layer L0 duringrecording of data. In other words, when recording is performed on thesecond recording layer L1, a recording light beam passes through thefirst recording layer L0, resulting in a difference in the transmittancebetween pit portions and groove portions.

[0010] Light power was measured for an optical recording medium at amirror area, a pit area, a groove area and a groove area with marks, forsimulation of the light power depending on a difference in thetransmittance according to various conditions of the first recordinglayer L0, as shown in FIGS. 3A through 3D. Here, the number of trackstrapped by laser beam transmitted through a lens was taken intoconsideration.

[0011] Tables 1 and 2 list input parameters and items forexperimentation. In Table 1, Rc represents the reflectivity of acrystallized portion of a recording layer and Ra represents thereflectivity of an amorphous portion of a recording layer. TABLE 1Parameter Condition Wavelength (nm) 400 Numerical Aperture (NA)0.65/0.85 Minimum mark length (μm) 0.275/0.194 Modulation EFM+(Eight-to-Fourteen Modulation-plus) Track pitch (TP) (μm) 0.30, 0.34,0.38 Reflectivity (%) Rc = 25, Ra = 5

[0012] TABLE 2 Item Factor Example Dual recording layer Structure offirst recording Mirror, pits, grooves, , layer grooves with marks. HighNA Number of tracks trapped  85 for 0.65 of NA by laser beam 160 for0.85 of NA Incident angle of beam 40.5° for 0.65 of NA 58.2° for 0.85 ofNA

[0013]FIG. 4 is a graph showing the measurement result of light powerdepending on the transmittance for the cases shown in FIGS. 3A, 3B, 3Cand 3D. With reference to FIG. 4, according to the simulation result, adecrease in the light power is smallest in the mirror portion (graphline with solid squares), and the light power gradually decreases morein the order of a pit portion (graph line with solid diamonds), a grooveportion (graph line with solid triangles block) and a groove markportion (graph line with solid circles). Therefore, as shown in FIG. 4,in the case of a dual layer disc, the transmittance varies according tothe physical geometry of the first recording layer L0, which in case ofa rewritable optical recording medium can further affect the recordingpower during recording of data.

SUMMARY OF THE INVENTION

[0014] To solve the above problems, it is an object of the presentinvention to provide an optical recording medium having a lead-out areaconfigured to prevent a pickup from deviating from a user data areaduring recording and/or reproduction of data, without affecting therecording power. The present invention can be applied to opticalrecording media, which include optical rewritable recording media. Inparticular, in case of multi-layer optical recording media the presentinvention unifies the physical geometry of a recording layer as well asprovides a discriminating lead-out area. For example, in a dual layerrewritable optical recording media, the present invention unifies thephysical geometry of a first recording layer L0 of the dual layer disc(i.e., wobbles formed on at least one lateral surface of each grooveprovide a uniform transmittance of an optical light beam passing througha recording layer) as well as newly defines a lead-out area or a middlearea to perform a guard function. A middle area means each outercircumference of the first and second recording layers in oppositetracks. That is, the opposite tracks are sequentially addressed from theinner circumference of the first recording layer L0 to the outercircumference thereof, and then from the outer circumference of thesecond recording layer L1 to the inner circumference thereof.

[0015] Additional objects and advantages of the invention will be setforth in part in the description which follows and, in part, will beobvious from the description, or may be learned by practice of theinvention.

[0016] Accordingly, to achieve the above and other objects of theinvention, there is provided an optical recording medium having a userdata area and a lead-out area, wherein the user data area and thelead-out area each has grooves and lands formed thereon, wobbles areformed on at least one lateral surface of each of the grooves, and thewobbles of the lead-out area have different characteristics from thoseof the user data area.

[0017] Further, the wobbles of the lead-out area are formed bymodulating at least one feature of frequency, period, amplitude andphase of the wobbles of the user data area.

[0018] Further, the wobbles may include addressing information orreference time information in the form of phase locked loop (PLL).

[0019] Further, in addition to the different wobbles in the user dataarea and the lead out area, synchronization patterns of signals readfrom the grooves of the user data area and the lead-out area aredifferent.

[0020] Further, in addition to the different wobbles in the user dataarea and the lead-out area, predetermined recording patterns arerecorded on the outermost circumference of the optical recording mediumto prevent an optical pickup from deviating from the user data areaduring recording and/or reproduction of data.

[0021] In another aspect of the present invention, there is provided anoptical recording medium having a user data area and a lead-out area,wherein predetermined recording patterns are recorded on the outermostcircumference of the optical recording medium to prevent an opticalpickup from deviating from the user data area during recording and/orreproduction of data.

[0022] Another aspect of the present invention provides an opticalrecording medium having a user data area and a lead-out area, whereinthe user data area and the lead-out area each has grooves and landsformed thereon, and different types of synchronization patterns are usedin the lead-out area and the user data area.

[0023] Also, two or more recording layers may be provided formulti-layer recording.

[0024] Further, in case of multi-layer recording media, the two or morerecording layers have different recording patterns in their lead-outareas.

[0025] Further, in case of multi-layer recording media, the two or morerecording layers have different synchronization patterns in theirlead-out areas.

[0026] Further, in the case of multi-layer recording media, the lead-outarea has a width of two or more times the maximum allowance of disceccentricity.

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The above objects and advantages of the present invention willbecome more apparent by describing in detail example embodiments thereofwith reference to the attached drawings in which:

[0028]FIG. 1 shows an enlarged view illustrating portions A, B and C ofa conventional optical recording medium;

[0029]FIG. 2 is a partially cross-sectional view illustrating aconventional optical recording medium;

[0030]FIGS. 3A through 3D illustrate various portions of theconventional optical recording medium;

[0031]FIG. 4 illustrates the experimental result of light power forvarious cases; and

[0032]FIG. 5 is an enlarged view illustrating portions A, B and C of anoptical recording medium according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] Hereinafter, example embodiments of the present invention will bedescribed in detail with reference to the attached drawings where likereference numerals refer to the like elements throughout. Theembodiments are described below to explain the present invention byreferring to the figures and to more completely explain the presentinvention to anyone skilled in the art. The present invention is notrestricted to the following embodiments, and many variations arepossible within the spirit and scope of the present invention, the scopeof which is defined in the claims and their equivalents.

[0034] Referring to FIG. 5, an optical recording medium according to thepresent invention includes a lead-in area 100, a user data area 120 anda lead-out area 130, each area having grooves 123 and lands 125 formedthereon. Wobbles 105 and 135 are formed on at least one lateral surfaceof each of grooves 123 and lands 125 in the user data area 120 and thelead-out area 130. Here, a portion “E” of the user data area 120 and aportion “D” of the lead-out area 130 are enlarged and shown in FIG. 5.Reference numeral 110 denotes a laser beam.

[0035] As described above, the lead-out area 130 has a guard functionthat prevents an optical pickup (not shown) from deviating from the userdata area during recording and/or reproduction of data, and in case of adual-layer disc the lead-out area can keep/maintain tracking whileinterlayer jumping from the outermost circumference.

[0036] In an optical recording medium according to a first embodiment ofthe present invention, to provide the guard function, wobbles differentfrom the wobbles 105 in the user data area 120 are formed in an areabeyond a predetermined radius of the optical recording medium (i.e., alead-out area). In other words, at least one kind of features includingperiods, frequencies, amplitudes and phases of the wobbles 105 and 135are modulated in the user data area 120 and the lead-out area 130. Thewobbles may include addressing information or reference time informationin the form of phase locked loop (PLL).

[0037] For example, the wobbles of the lead-out area 130 can be formedby modulating at least one feature of frequency, period, amplitude andphase of the wobbles of the user data area 120 as follows. In case ofmodulating the frequencies of the wobbles 105 and 135, the wobble 135 ofthe lead-out area 130 may be formed to have a frequency of n times (n isa real number) the basic frequency of the wobble 105 of the user dataarea 120. The differing wobbles of the user data area 120 and the leadout area 130 unify the physical geometry of the optical recording mediumas well as provide a discriminating lead-out area as a guard. In otherwords, the wobbles formed on at least one lateral surface of each grooveaccording to the present invention provide a uniform transmittance of anoptical light beam passing through a recording layer. For example, tounify the physical geometry of the disc and to serve as a guard, thelead-out area 130 may be configured such that the wobble 135 has afrequency of 2 times that of the user data area 120.

[0038] Further, in case of modulating the wobble period T, the wobble105 of the user data area 120 and the wobble 135 of the lead-out area130 can, for example, have periods 200T and 100T, respectively, so thatthe lead-out area 130 can be discriminated.

[0039] Further, after completion of manufacture of the disc, 00h aspattern data may be recorded in the lead-out area 130. Accordingly, the00h pattern data is read out by a channel 1 (Ch1) duringrecording/reproduction, and the wobble frequency and/or period can beread out by a channel 2 (Ch2), thereby allowing double discrimination ofthe lead-out area 130.

[0040] In an optical medium according to a second embodiment of thepresent invention, when formatting the optical medium, a predeterminedrecording pattern can be recorded in the lead-out area 130, therebydiscriminating the lead-out area 130.

[0041] The predetermined recording pattern may be, for example, arecording pattern used in the user data area 120. That is to say, amongrecording patterns used in the user data area 120, a predeterminedrecording pattern, for example, a 00h pattern, can be repeatedlyrecorded in the lead-out area 130, thereby recognizing the lead-out area130.

[0042] Alternatively, the recording pattern not used in the user dataarea 120 is recorded in the lead-out area 130, thereby recognizing thelead-out area 130. For example, a 00h pattern is recorded in the userdata area 120 and an FFh pattern as another pattern is recorded in thelead-out area 130. Therefore, in this case, the recording patternsrecorded on the lead-out area 130 are different from those used in theuser data area 120. Here, the 00h and FFh patterns are recordingpatterns based on the hexadecimal system.

[0043] According to a third embodiment of the present invention, theoptical medium includes a user data area 120 and a lead-out area 130,each having grooves 123 and lands 125. Different types ofsynchronization patterns (to be abbreviated as “sync patterns”hereinafter) are used in the user data area 120 and the lead-out area130. Thus, the lead-out area 130 is discriminated by recognizing thesync patterns, thereby preventing an optical pickup from deviating fromthe user data area 120 during recording/reproduction. The sync patternsare recorded on the grooves.

[0044] As described above, in an optical recording medium, differenttypes of wobbles are formed on the grooves of the user data area or thelead-out area, thereby preventing an optical pickup that performsrecording/reproduction from deviating from the user data area. Further,in an optical recording medium predetermined recording patterns and/ordifferent synchronization patterns can be recorded on the lead-out areaand the user data area alone or in addition to the different typewobbles to provide a guard function preventing deviation of the pickupfrom the user data area. The recording and synchronization patterns inaddition to the wobbles can allow double discrimination of the lead-outarea. Thus, in the present invention, an optical pickup can be preventedfrom deviating from the user data area 120 by discriminating between theuser data area 120 and the lead-out area 130.

[0045] The present invention can accommodate a multi-layer opticalrecording medium having two or more recording layers as follows. Themulti-layer optical recording medium includes a user data area 120 and alead-out area 130, each having grooves 123 and lands 125. Wobbles 105and 135 are formed on at least one lateral surface of each of thegrooves 123 and the lands 125. The wobbles 105 and 135 may includeaddressing information or reference time information, e.g., phase lockedloop (PLL). To prevent an optical pickup from deviating from the userdata area 120, the wobbles 105 and 135 formed in the user data area 120and the lead-out area 130, respectively, may be modulated into differenttypes of wobbles.

[0046] Further, in a multi-layer optical recording medium having two ormore recording layers, different recording patterns are formed on eachlead-out area of the respective recording layers, thereby discriminatingthe respective recording layers. For example, in the case of adual-layer recording medium, a 00h pattern may be recorded on thelead-out area of the first recording layer and an FFh pattern may berecorded on the lead-out area of the second recording layer. By doingso, the recording patterns are read out by a channel 1 (Ch1) and wobblesignals based on wobble modulation are read out by a channel 2 (Ch2),during recording and/or reproducing on/from the optical recordingmedium.

[0047] Further, to maintain tracking during interlayer jumping, thewidth of the lead-out area 130 may be determined to be twice or moretimes the maximum allowance of disc eccentricity. If disc eccentricityaccording to injection in the course of manufacture of a disc isapproximately 50 μm, the width of the lead-out area 130 is determined tobe 100 μm or greater.

[0048] According to another embodiment of the present invention, todiscriminate the respective recording layers in a multi-layer opticalrecording medium having two or more recording layers, different syncpatterns may be used for each recording layer in the lead-out area 130.

[0049] As described above, according to the present invention, groovesare formed on a user data area and a lead-out area, and different typesof wobbles are formed on the grooves of either the user data area or thelead-out area, thereby configuring a recording layer of a multi-layerrecording medium to have a same condition and providing a discriminatinglead-out area. The discriminating lead-out area prevents an opticalpickup that performs recording/reproduction from deviating from the userdata area. Also, the configuration of the whole area of a recordinglayer to have the same condition, prevents deterioration in reproductionand/or recording due to a difference in light power transmittance ofanother higher (upper) recording layer. For example, in a dual layeroptical recording medium, the whole area of a first recording layer isconfigured to have a same condition to prevent deterioration inreproduction and/or recording, which requires light power adjustment, ona second layer due to a difference in a transmittance of the firstrecording layer. Therefore, in case of a multi-layer rewritable opticalrecording medium according to the present invention, recording can beperformed on the grooves 123 or on both the grooves 123 and the lands125 and the optical pickup can maintain a uniform light power duringreproduction and/or recording on respective recording layers.

[0050] By using such wobbles according to the present invention, a wholearea of a recording layer can be configured to have a same condition,preventing deterioration in reproduction and/or recording due to adifference in the transmittance of a recording layer. Although the wholearea of the recording layer is configured to have the same condition, inthe present invention, an optical pickup can be prevented from deviatingfrom the user data area 120 and the respective recording layers can bediscriminated by using the wobbles according to the present inventionand/or the above described recording and synchronization patterns.

[0051] While this invention has been particularly shown and describedwith reference to example embodiments thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the spirit and scope of theinvention as defined by the appended claims.

What is claimed is:
 1. A multi-layer optical recording medium,comprising: user data areas on each recording layer; grooves formed onthe user data areas; user data wobbles formed on at least one lateralsurface of each groove of one of the recording layers; and lead outwobbles, which differ from the user data wobbles of the one recordinglayer, formed in an area beyond a predetermined radius of the onerecording layer.
 2. The multi-layer optical recording medium accordingto claim 2, wherein the wobbles of the lead-out area of the onerecording layer are formed by modulating at least one feature offrequency, period, amplitude and phase of the wobbles of the user dataarea of the one recording layer.
 3. The multi-layer optical recordingmedium according to claim 3, wherein recording is performed on thegrooves and/or lands formed on the user data area of the one recordinglayer and the area beyond the predetermined radius of the one recordinglayer.